Researchers from the Mayo Clinic, presenting at the 9th International Conference on Alzheimer's Disease and Related Disorders, have cast doubt on the incidence of "pump head" - cognitive disorders seen after coronary artery bypass grafting. A previous study from Duke University suggested that more than one third of bypass patients had at least a 20% drop in cognitive abilities after surgery, and the impairment persisted for at least 5 years.
These studies have been criticized for, among other things, not having a suitable control group. The Mayo researchers attempted to remedy this shortcoming by identifying a group of 564 patients with dementia, then comparing the incidence of prior bypass surgery to the incidence of bypass surgery in a control group of 493 patients without dementia. (Patients were identified for this study by reviewing the medical records of patients in the Rochester Epidemiology Project.)
They found no significant difference in the incidence of prior bypass surgery among dementia patients and control patients. This result indicates that, at the least, the rolls of patients with the clinical diagnosis of dementia are not being swollen by bypass-surgery-induced cognitive impairment.
However, it ought to be noted that in the original Duke study many of the patients who were found to have cognitive impairment had relatively subtle problems, and might not have been identified as having "dementia" unless specific testing had been done. The Rochester study would have missed such patients altogether.
So, while this new study ought to give a certain amount of comfort to patients who have had or who might need to have bypass surgery, it does not put the issue to rest.